When molded bodies are prepared from silicon or germanium granular material, the particles of the granular material are joined together by sintering, to produce a consolidated material, having the desired three-dimensional shape. Another method requires the particles of the granular material to be melted superficially, for example, by means of an electron beam, to join the contacting surfaces, so that they consolidate upon cooling down. In these processes where the granular material has to be heated to temperatures in the region of their melting point, the material may become contaminated from binders. According to a further known process, the granular silicon material is brought into contact with a silicon etching agent, wherein the particles of the granular material consolidate to form a molded body as a result of reaction bonding to each other. However, in this case, an oxide layer is formed on the individual particles, which makes the material inherently unsuitable for applications in which a low oxygen content is important.
In another known process, the particles of the granular material are mixed with carbonizable substances and after thermal treatment, are joined by the carbon to form a molded body. The resultant material is generally unsuitable for applications requiring high purity because of its carbon content. In many of the known processes, the use of fine granular material, i.e., of granular material with a mean particle size of less than 1 mm, is often difficult because of its handling problems.